Sound reproducing apparatus



Sept. 26, 1939. H. F. OLSON SOUND REPRODUCING APPARATUS Filed April 50,1937 2 SheetsSheet 1 WV 3 & W S? n My w .m y & QR UUU N. q UUU H aminimum w Qk if. w T m Q Q 3 \E Sept. 26, 1939. H. F. OLSON 2,174,163

SOUND REPRODUCING APPARATUS Filed April 3D. 1937 2 Shuts-Sheet 2Zhwentor I Gttorneg Patented Sept. 26, 1939 PATENT OFFICE 2,174,103SOUND mzraonucmo APPARATUS Harry F. Olson,

Audubon, N. J assignor to Radio Corporation of America, a corporation ofDelaware Application April 30, 1937, Serial No. 140,023

18 Claims.

This invention relates to sound reproducing apparatus, and moreparticularly to a horn loudspeaker system for .use in theaters as partof the talking moving picture reproducing equipment.

The desirability of placing immediately behind I a moving picture screenone or more loudspeakers in order to create the illusion that thecharacters portrayed on the sound has long been recognized. It has alsobeen recognized that horn loudspeakers have certain inherent advantagesover the direct radiator flat baiiie type, and for this reason hornloudspeakers have been generally adopted in theater sound reproducingsystems, a plurality of horns being usually employed to obtain uniformdirectional characteristics.

Placing the horn loudspeakers behind the screen necessitates theirremoval each time the screen is raised for a stage presentation andtheir subsequent replacement when the screen is lowered. In order toreduce the bulk of the horns and to facilitate handling, compound hornspeakers have been used wherein the high frequencies are reproducedthrough one or more short horns having small throats and rapid flares,and the low frequencies are reproduced through a long, folded hornhaving alarge throat and a small rate of flare. While a compound horn ofthis type also has, among other advantages, those of greater over-allefliciency than the single horn because of the smaller range covered byeach horn and smaller space requirement, it has the disadvantage ofphase difference between the sound emanating from the two units due todifference in path length, as well as other disadvantages resulting fromfilters usually employed to discriminate betweenthe signal energysupplied to each of the units. The latter disadvantages, among others,therefore make it desirable to 40 use a single horn system for eachdriver.

In my copending application, Serial No. 139,848, filed April 30, 1937, Ihave disclosed and claimed a novel straight-axis, single-hornloudspeaker which has the advantages of the multi-hom sys- 45 temsdescribed above without having their dis-.

advantages. A single horn loudspeaker must, however, be made very longif it is to cover a wide range within the audio spectrum, and making thehorn long imposes the serious limitation noted before of rendering itdifficult to move the loudspeaker out of sight when the screen is raisedfor a stage presentation. The horn or horns, as the case may be, can, ofcourse, be mounted to fly with the screen. However, long horns not onlymake it difficult to raise the screen, but also defscreen are actuallyemitting initely limit the distance that the screen may be raised. i

The primary object of my present invention is to provide an improvedhorn loudspeaker system for theater and like use which will not besubject to the aforementioned difficulties.

More specifically, it is an object of my present invention to provide animproved horn loudspeaker system for theater and like use which willrequire a minimum of space behind the screen.

Another object of my present invention is to provide an improved hornloudspeaker system as aforesaid which can be mounted for ready and easyflying with the screen.

Still another object of my present invention is to provide an improvedmulti-horn loudspeaker system for theater and similar use which issimple in construction, which can readily be manipulated, and which ishighly efficient in use.

In accordance with my present invention, I arrange a cluster of hornloudspeakers in three rows with each row in a plane substantially atright angles to the screen, and hinge adjacent rows to each other in amanner such that the several rows of horns may be unfolded into a singlerow in a plane at an angle to that of the screen. The middle row is alsohingedly connected to the framework on which the screen is mountedwhereby, after the several rows of horns are unfolded, they may all beswung about the hinge connection of the middle row to lie in a planeparallel with and close to the screen. During the showing of a picture,the horns are in their folded position behind the screen with their axesextend ing away from the screen, but when the screen is to be raised,the horns are unfolded and swung into position against the screen withtheir axes in a plane parallel thereto. When in unfolded positionagainst the screen, the horns extend to the rear of the screen adistance equal substantially to the greatest mouth dimension of theindividual horns, which is far less, of course, than the length of eachhorn. This permits flying the horns with the screen without anydifllculty and with a minimum space requirement behind the screen.

The novel features that I consider characteristic of my invention setforth with particularity in the appended claims. The invention itself,however, both as to its organization and method of operation, togetherwith additional objects and advantages thereof, will best be understoodfrom the following description, when read in connection with theaccompanying drawings, in which Figure 1 is a rear elevation of a hornloudlit . of cross-pieces speaker system with the horn cluster foldedand in reproducing position,

Figure 2 is a similar view but showing, in dotand-dash lines, the horncluster partly unfolded, and in solid lines, the horn cluster fullyunfolded,

Figure 3 is a similar view showing the unfolded horn cluster in raisedposition against the screen, this figure also showing mechanism forautomatically raising the horns to the position shown, and

Figure is a fragmentary detail view of a slightly modified iorm ofcoupling between the several rows of horns.

Referring more specifically to the drawings, wherein similar referencecharacters designate corresponding parts throughout, there is shown asupporting framework 6 made rigid by a plurality i3 having a suitable,plane, sound-porous screen ii stretched over the front thereof invertical position. Hin edly connected to one of cross-pieces 3 (forexample, the middle one), a row 0; long, straighter-us loudspeaker hornsl, each of which, may be driven by an individual driver of suitabledesign, such as an electrodynamic signal translating device (not shown).The row of horns i normally lies in a substantially horizontal plane, ora plane substantially normal to the screen 5, and the respective hornsare preferably of the type disclosed my above-identified copendingapplication.

Associated with the middle row of horns l and also lying insubstantially horizontal planes are a top row of horns 9 and a bottomrow of horns Ii, the several horns of the three respective rowsconstituting a horn cluster for amplifying sound produced in conjunctionwith the subject matter portrayed upon the front of the screen The hornrow 9 is hingedly connected to the middle row I along the edge 7athereof, while the bottom row is'hingedly connected to the middle row ialong the diagonally opposite edge lb thereof. Thus, the horn rows 9 andi may each be swung in a counter-clockwise direction, as viewed in thedrawings, to bring the latter two horn rows into coplanar relation withthe middle horn row 7. After being brought into this relation, theunfolded horn cluster may then be raised to lie in a plane substantiallyparallel with and close to the screen 5, as shown in Fig. 3.

For manipulating the several rows of 'horns, I provide a series of linesor other suitable flexible elements A, B, C and D which are trainedaround a number of pulleys |3. The line A is connected to the throat endof the middle horn of the row I, as clearly shown in Fig. 2, while theline B is connected to a corner of the mouth end of that horn in rowwhich'is most remote from the hinge connection 11). The line C is alsoconnected to the same point on the last named horn as the line B, whilethe line D is connected to the mouth end of that horn of row ,9 which ismost remote from the hinge connection 1a. In operation, the line A isfirst pulled to raise the horn row 9 substantially to the dot-and-dashline position shown in Fig. 2 after which both lines A and B are pulledtogether. This raises the entire horn cluster slightly about the hingeconnection between the horn row I and the middle cross-piece 3 tofreethe lower horn row H from a supporting ledge |5 which supports theweight of the entire horn cluster when in the position shown in Fig. 1.Continued pull on the lines A and B, with a somewhat faster pull on theline B than on the line A, will then raise the unfolded horn cluster tothe position shown in Fig. 3, the horn rows 9 and ii meanwhile fallinginto coplanar relation with the horn row I and the aligned horn rowscoming to rest in a plane substantially parallel with the screen 5. Tolower and refold the horn cluster, the lines A and B are graduallyslackened, with the line B slackened somewhat faster than the line A,until the unfolded cluster has reached a position somewhat above thesolid line position automatically, and for this pill. .L so free ends ofthe lines A, C e a plurality of individual bell-cranlrs it, ea h 1 uotally mounted on a shaft i9. Fined to motor driven shaft 2i are aplurality of cams 25, ill and with which the opposite ends of thebellcranks ii are in engagement and which are suitably shaped to effectthe operations heretofore set forth and in the sequence set forth. Themotor (not shown) for operating the cam shaft 2| may be mounted on anextension of the base of the framework I, so that the entire mechanism,together with the raised horn cluster, may be flown with the screen byconventional means at present in use for this purpose.

In Fig. 4, I have shown another arrangement for unfolding the horncluster prior to raising the unfolded cluster to the elevated position.In this arrangement, a relatively large sun gear 3| ls fixed to themiddle row of horns l in axial alignment with the axis of the hinge la.At a suitable point on the row of horns 9 is mounted a motor 33 to therevoluble shaft of which is fixed a relatively small gear 35 which is inmesh with the gear 3|. By causing the shaft of the motor 33 to rotate inthe proper dlrection, the gear 35 wlll move about the sun gear 3| as aplanet, and this will carry the horn row 9 around with it into 00-planar relation wlth the horn row I. A sun gear similar to the gear 3|may be mounted on the diagonally opposite corner of the horn row 1 forcooperation with another planet gear 35 carried by the horn row IReversing the rotation of the motor shaft will, of course, refold thehorn cluster.

Although I have shown and described several modifications of myinvention, it will be apparent to those skilled in the art that manyother modifications thereof andchanges in those shown and described arepossible. For example, in place of a. cluster of horns, a single, long,stra|ght-axls horn may be employed, and it may be arranged either toswing in a vertical plane from a position with its axis normal to thescreen to a position where its axis is substantlally'parallel thereto,or it may ing position, the space requirement behind the screen when thescreen duced to only the greatest dimension of the mouth of the horn,regardless ofthe number of horns used. It will also be obvious to thoseskilled in the art that, where an arrangement such as that shown in Fig.4 is employed, for example, the unfolded horn cluster may be raised bythe same mechanism which flies the screen through a suitable arrangementof block and tackle in the balanced harness conventionally employed forflying the screen. Many other changes and modifications will, no doubt,readily suggest themselves to those skilled in the art. I thereforedesire that my invention shall not be limited except insofar as is madenecessary by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In combination, a moving picture screen, and a cluster of loudspeakerhorns'associated therewith, said cluster comprising a plurality ofrowsof individual horns of which each row is pivotally connected to itsadjacent rows in a manner to permit unfolding said cluster into a singlerow.

2. In combination, a moving picture'screen, and

a cluster of loudspeaker horns associated therewith, saidclustercomprising a plurality of rows of individual horns of which eachrow normally lies in a plane substantially normal to the screen, andeach of said rows being hingedly connected to its adjacent rows in amanner to permit unfolding said cluster into a single row in coplanarrelation. Y

3. In combination, a supporting framework, a moving picture screensupported thereby, and a cluster of loudspeaker horns associated withsaid screen, said cluster comprising a plurality ofrows of individualhorns of which each row is hingedly connectedto its adjacent rows topermit unfolding of said cluster into a single row,

and one of said rows being hingedly connected to said framework topermit swinging the unfolded cluster as a unit relative to said screen.

4. In combination, a supporting framework, a moving picture screensupported thereby, and a cluster of loudspeaker horns associated withsaid screen, said cluster comprising a plurality of rows of individualhorns of which each row normally lies in a plane substantially normal tothe screen and of which each row is hingedly connected to its adjacentrows to permit unfolding of saidcluster into a single row in coplanarrelation, and one of said rows being hingedly connected to saidframework to permit swinging the unfolded cluster as a unit into a planesubstantially parallel with said screen.

-5. The invention set forth in claim 4 characterized in that said screenlies in a vertical plane, characterized further in that each of saidrows of horns lies in a substatnially horizontal plane when the clusteris in normally-folded condition, and characterized still further in thatsaid cluster is free to be swung into a substantially vertical planeclosely adjacent said screen.

6. The invention set forth in claim 4 characterized in that said clustercomprises three rows of horns each lying in a substantially horizontalplane when the cluster is in normally-folded condition, characterizedfurther in that the top row is hingedly connected to the middle row forswinging movement in one direction relative thereto in a clockwise senseand the bottom row is hingedly connected to said middle row for swingingmovement in the same direction relative thereto in a clockwise sensewhereby said is to beflown is re-- top and bottom rows may be swung intocoplanar relation with said middle row, and characterized still furtherin that said middle row is the one which is hingedly connected to saidframework.

7. 'In combination, a supporting framework, a moving picture screensupported thereby, a clus- -ter of loudspeaker horns associated withsaid screen, sa d cluster comprising a plurality of rows of individualhorns of which each row is hingedly connected to its adjacent rows topermit unfolding of said cluster into a single row in coplanar relation,one of said rows being hingedly connected to said framework to permitswinging the unfolded cluster as a unit relative to said screen intoanother plane, and means for unfolding said cluster and swinging it intosaid last named plane. 8. In combination, a supporting framework, amoving picture screen supported thereby, a cluster of loudspeaker hornsassociated with said screen, said cluster comprising a plurality of rowsof individual horns of which each row normally lies in a planesubstantially normal to the screen, each of said rows of horns beinghingedly connected to its adjacent rows to permit unfolding of saidcluster into a single row in coplanar relation, one of said rows beinghingedly connected to said framework to permit. swinging the unfoldedcluster as a unit relative to said screen, and means for unfolding saidcluster and swinging the unfolded cluster into a plane substantiallyparallel with said screen- 9. The invention set forth in claim 8characterized by the addition of means for supporting said cluster onsaid frame when in normallyfolded condition.

10. The invention set forth in claim 8 characterized in that saidunfolding and swinging means is adapted also to return the unfoldedcluster and refold said cluster to normal position.

11. The invention set forth in claim 8 characterized in that saidunfolding and swinging means comprises a plurality of flexible elementsconnected to the respective rows of horns and cam means for operatingsaid flexible elements, and

' characterized further in that said cam means also controls the returnof the unfolded cluster and the refolding of said cluster to normalposition.

12. In a horn loudspeaker system, the combination of a plurality ofhorns hingedly connected to each other to permit swinging of said hornsrelative to each other.

13. In a horn loudspeaker'system, the combination of a plurality ofhorns arranged in a plurality of rows, each of said rows being hingedlyconnected to its adjacent rows to permit unfolding of said rows into asingle, coplanar row.

-14. In a horn loudspeaker system, the combination of a plurality ofhorns arranged in three rows, one of said rows being hingedly connectedto the middle row along one edge thereof for swinging movement in onedirection relative thereto in a clockwise sense, and the third rowbeing. hingedly connected to said middle row along the diagonallyopposite edge thereof for swinging movement relative thereto in the samedirection in a clockwise sense, whereby said first and third rows syswmcomprising a cluster of horns arranged a M 2, plmality 0i" mws cm?individual horlzas which each raw is pivotaily cmnected to its adjacentrows in a manner w permit unfolding said cluster single mw cnplanarrelation, means piv-

